Role of Ca2+-activated K+ Channels in Breast Cancer Proliferation and Resistance to Cytotoxic Drugs and Radiation

我们在遗传小鼠肿瘤模型中的分析表明，大电导（BK）和中等电导（SK 4或IK）的Ca 2+激活的K+通道（KCa）在肿瘤细胞增殖和迁移中起重要作用。以前，我们已经将乳腺癌（MMTV/c-neu）、胶质母细胞瘤（NF 1/TRP 53）和前列腺癌（TRAMP）的三种遗传小鼠模型分别与BK-/-和SK 4-/-小鼠杂交。由MRI/PET支持的Kaplan-Meier分析显示，BK-/-小鼠中完全预防乳腺肿瘤发作和进展，SK 4-/-小鼠中部分抑制乳腺肿瘤发作和进展。在胶质母细胞瘤模型中，BK-/-动物的生存期延长了90天，而携带前列腺癌的小鼠没有从BK或SK 4消融中显著受益。因此，我们将研究SK 4和BK通道阻断剂预防肿瘤生长和克服MMTV/c-neu肿瘤的治疗抗性的潜力。对其他乳腺癌模型（例如MMTV/PyMT）的分析将显示BK和SK 4消融在MMTV/c-neu小鼠中的保护作用是否对乳腺肿瘤的发生和进展具有普遍重要性。为了识别细胞和分子机制，我们将使用天然肿瘤组织和原发性肿瘤细胞来表征例如Ca 2+信号传导、细胞周期过程和细胞毒性药物以及在不存在和存在KCa阻断剂的情况下的辐射反应。为了验证体内效应是由肿瘤细胞的KCa缺乏引起的，而不是间接介导的受体小鼠血管形成或免疫应答的差异，将通过将原代肿瘤细胞转移至BK-/-和SK 4-/-小鼠进行同种异体移植研究。在这一系列中，在MMTV-Cre-小鼠中产生的肿瘤特异性BK突变体也将使我们能够将BK失活的主要抗肿瘤作用与次要抗肿瘤作用分开。此外，免疫受损小鼠将用作肿瘤移植受体以繁殖KCa缺陷型和野生型原发性肿瘤及其衍生的细胞。通过比较移植物的生长及其对不同化疗和放疗方案的抗性，可以评估KCa对药物干预的重要性。

Our analyses in genetic mouse tumor models suggest an important role of Ca2+-activated K+ channels (KCa) of big (BK) and intermediate (SK4 or IK) conductance in tumor cell proliferation and migration. Previously, we have interbred three genetic mouse models for mammary carcinoma (MMTV/c-neu), glioblastoma (NF1/TRP53) and prostate carcinoma (TRAMP) with BK-/- and SK4-/- mice, respectively. Kaplan-Meier-analyses supported by MRI/PET, showed in BK-/- mice a complete prevention and in SK4-/- mice a partial suppression of mammary tumor onset and progression. In the glioblastoma model the survival of BK-/- animals was prolonged by 90 days, while prostate cancer-bearing mice did not significantly benefit from BK or SK4 ablation. Hence, we will investigate the potential of SK4 and BK channel blockers to prevent tumor growth and overcome therapy resistance of MMTV/c-neu tumors. The analysis of additional breast cancer models (e.g. MMTV/PyMT) will show whether the protective effects of BK and SK4 ablation in MMTV/c-neu mice are of general importance for mammary tumor onset and progression. Aiming toward the identification of the cellular and molecular mechanisms, we will use native tumor tissues and primary tumor cells to characterize e.g. Ca2+ signaling, cell cycle processes and cytotoxic drug and irradiation responses in the absence and presence of KCa blockers. To validate that the in vivo effects are caused by KCa deficiency of tumor cells and not indirectly mediated differences in vascularization or immune responses of the recipient mice, allotransplantation studies will be performed by transferring primary tumor cells to BK-/- and SK4-/- mice. In this line, tumor-specific BK mutants generated in MMTV-Cre-mice will also allow us to separate primary from secondary anti-tumor effects of BK inactivation. Furthermore, immunocompromised mice will be used as tumor transplant recipients to propagate KCa-deficient and wild-type primary tumors and cells derived thereof. By comparing the growth of the engraftments and their resistance to different chemo- and radiotherapy regimes, the importance of KCa for a pharmacological intervention can be evaluated.